In an optical disc such as a DVD, the total storage capacity can be increased by providing two or more recording layers. To perform recording and reproducing operations, the optical disc is accessed from one side, and the focal point of an optical light beam from an optical head (pickup) is irradiated onto each of the recording layers. Accordingly, large-capacity recording/reproducing can be performed without turning the optical disc over. Particularly, with regard to DVDs, there are already two-layer discs that are practically being used, which are read-only type discs (ROM).
Patent document 1 discloses an optical information medium that has a multilayer structure including a first recording layer and a second recording layer. This optical information medium includes plural tracks arranged in a helical or a concentric manner, and the tracks have plural sectors. Each sector includes address information. Specifically, a first recording layer includes address information starting at 0 to (S−1) [S represents the number of sectors in each of the first recording layer and the second recording layer], and a second recording layer includes address information starting at S to (S×2−1).
Patent document 2 discloses an optical information medium that is a two-layer medium. The address information in the second layer corresponds to the bit-inverted or sign-inverted version of the address information in the first layer.
Patent document 3 describes another two-layer medium. There are address marks common to both the first recording layer and the second recording layer, which address marks are arranged according to the recession/protrusion arrangement of different pit rows. The recording layer can be identified by detecting the pattern of reproduction signals of the address marks.
In an optical disc in which information can be recorded, the address information needs to be embedded beforehand in order to identify the current position and the recording target position even when there is no information recorded.
With the technology of patent document 1, the address information is sequentially embedded starting at zero in the first recording layer, assuming that the number of sectors in the first recording layer is S. In the second recording layer, the address information starts at S. However, nothing is disclosed about the specific optical method of embedding the address information in an empty optical disc. Furthermore, the optical format in which the address information is embedded needs to be a format that does not interfere with signals of the recording data (data to be recorded or data that have been recorded are hereinafter referred to as “recording data”) after the data are recorded. However, nothing is disclosed about this point either.
Furthermore, when the number of sectors S of the first recording layer varies according to the optical disc (for example, in a case where the disc system is different or the number of tracks is different, and therefore the storage capacity per layer varies according to the optical disc), the address information at which the second recording layer starts will not be known. Thus, the address information in the radial direction of the optical disc cannot be calculated only from the address information of the second recording layer. However, nothing is disclosed about this point either.
Furthermore, patent document 2 discloses a technology of allocating address information for a two layer optical information medium. However, nothing is specifically disclosed about allocating address information of a multilayer optical information medium including three or more layers.
In the invention disclosed in patent document 3, the address information is common to both layers, but the two layers have pit rows with different physical recessions/protrusions, and therefore the address information of the two layers can be distinguished. However, this invention is not applicable to a multilayer medium including three or more layers.    Patent document 1: Japanese Laid-Open Patent Application No. 2000-293947    Patent document 2: Japanese Laid-Open Patent Application No. 2004-295950    Patent document 3: Japanese Laid-Open Patent Application No. 2000-293889
Accordingly, there is a need for a multilayer optical information medium and an optical information processing apparatus therefor, and a program product and an information medium including the same, with which the address information in each information layer (recording layer) can be easily acquired for multilayer optical information media having various numbers of laminated information layers (recording layers).